Myung-Whan Suh

Effect of low-level laser treatment on cochlea hair-cell recovery after ototoxic hearing loss

Abstract. The primary cause of hearing loss includes damage to cochlear hair cells. Low-level laser therapy (LLLT) has become a popular treatment for damaged nervous systems. Based on the idea that cochlea hair cells and neural cells are from same developmental origin, the effect of LLLT on hearing loss in animal models is evaluated. Hearing loss animal models were established, and the animals were irradiated by 830-nm diode laser once a day for 10 days. Power density of the laser treatment was 900u2009u2009mW/cm2, and the fluence was 162 to 194 J. The tympanic membrane was evaluated after LLLT. Thresholds of auditory brainstem responses were evaluated before treatment, after gentamicin, and after 10 days of LLLT. Quantitative scanning electron microscopic (SEM) observations were done by counting remaining hair cells. Tympanic membranes were intact at the end of the experiment. No adverse tissue reaction was found. On SEM images, LLLT significantly increased the number of hair cells in middle and basal turns. Hearing was significantly improved by laser irradiation. After LLLT treatment, both the hearing threshold and hair-cell count significantly improved.

Gap prepulse inhibition of the auditory late response in healthy subjects

The gap-startle paradigm has been used as a behavioral method for tinnitus screening in animal studies. This study aimed to investigate gap prepulse inhibition (GPI) of the auditory late response (ALR) as the objective response of the gap-intense sound paradigm in humans. ALRs were recorded in response to gap-intense and no-gap-intense sound stimuli in 27 healthy subjects. The amplitudes of the baseline-to-peak (N1, P2, and N2) and the peak-to-peak (N1P2 and P2N2) were compared between two averaged ALRs. The variations in the inhibition ratios of N1P2 and P2N2 during the experiment were analyzed by increasing stimuli repetitions. The effect of stimulus parameter adjustments on GPI ratios was evaluated. No-gap-intense sound stimuli elicited greater peak amplitudes than gap-intense sound stimuli, and significant differences were found across all peaks. The overall mean inhibition ratios were significantly lower than 1.0, where the value 1.0 indicates that there were no differences between gap-intense and no-gap-intense sound responses. The initial decline in GPI ratios was shown in N1P2 and P2N2 complexes, and this reduction was nearly complete after 100 stimulus repetitions. Significant effects of gap length and interstimulus interval on GPI ratios were observed. We found significant inhibition of ALR peak amplitudes in performing the gap-intense sound paradigm in healthy subjects. The N1P2 complex represented GPI well in terms of suppression degree and test-retest reliability. Our findings offer practical information for the comparative study of healthy subjects and tinnitus patients using the gap-intense sound paradigm with the ALR.

A programmable acoustic stimuli and auditory evoked potential measurement system for objective tinnitus diagnosis research

This paper presents the development of a single platform that records auditory evoked potential synchronized to specific acoustic stimuli of the gap prepulse inhibition method for objective tinnitus diagnosis research. The developed system enables to program various parameters of the generated acoustic stimuli. Moreover, only by simple filter modification, the developed system provides high flexibility to record not only short latency auditory brainstem response but also late latency auditory cortical response. The adaptive weighted averaging algorithm to minimize the time required for the experiment is also introduced. The results show that the proposed algorithm can reduce the number of the averaging repetitions to 70% compared with conventional ensemble averaging method.

The gap-prepulse inhibition deficit of the cortical N1-P2 complex in patients with tinnitus: The effect of gap duration

ABSTRACT The present study aimed to investigate whether gap‐prepulse inhibition (GPI) deficit in patients with tinnitus occurred in the N1‐P2 complex of the cortical auditory evoked potential. Auditory late responses to the intense sound of the GPI paradigm were obtained from 16 patients with tinnitus and 18 age‐ and hearing loss‐matched controls without tinnitus. The inhibition degrees of the N1‐P2 complex were assessed at 100‐, 50‐, and 20‐ms gap durations with tinnitus‐pitch‐matched and non‐matched frequency background noises. At the 20‐ms gap condition with the tinnitus‐pitch‐matched frequency background noise, only the tinnitus group showed an inhibition deficit of the N1‐P2 complex. The inhibition deficits were absent in both groups with longer gap durations. These findings suggested that the effect of tinnitus emerged depending on the cue onset timing and duration of the gap‐prepulse. Since inhibition deficits were observed in both groups at the same 20‐ms gap condition, but with the tinnitus‐pitch‐non‐matched frequency background noise, the present study did not offer proof of concept for tinnitus filling in the gap. Additional studies on the intrinsic effects of different background frequencies on the gap processing are required in the future. HIGHLIGHTSWe evaluated the effect of tinnitus on the GPI of the N1‐P2 complex with various gap durations.The N1‐P2 complex with the GPI paradigm may reflect the presence of tinnitus with discreet selection of gap duration.The frequency‐dependent effects of background noise on the gap processing should be considered.

Safety assessment of trans-tympanic photobiomodulation

We evaluated functional and morphological changes after trans-tympanic laser application using several different powers of photobiomodulation (PBM). The left (L) ears of 17 rats were irradiated for 30xa0min daily over 14xa0days using a power density of 909.1 (group A, 5040xa0J), 1136.4 (group B, 6300xa0J), and 1363.6 (group C, 7560xa0J) mW/cm2. The right (N) ears served as controls. The safety of PBM was determined by endoscopic findings, auditory brainstem response (ABR) thresholds, and histological images of hair cells using confocal microscopy, and light microscopic images of the external auditory canal (EAC) and tympanic membrane (TM). Endoscopic findings revealed severe inflammation in the TM of C group; no other group showed damage in the TM. No significant difference in ABR threshold was found in the PBM-treated groups (excluding the group with TM damage). Confocal microscopy showed no histological difference between the AL and AN, or BL and BN groups. However, light microscopy showed more prominent edema, inflammation, and vascular congestion in the TM of BL ears. This study found a dose-response relationship between laser power parameters and TM changes. These results will be useful for defining future allowance criteria for trans-tympanic laser therapies.

Narrow band CE-Chirp auditory steady-state response is more reliable than the conventional ASSR in predicting the behavioral hearing threshold

OBJECTIVEnWe evaluated conventional ASSR (Bio-logic MASTER II) and NB CE-Chirp ASSR thresholds as objective hearing measures in both normal and hearing loss subjects.nnnMETHODSnPatients with sensorineural hearing loss and volunteer normal hearing subjects were enrolled. Pure tone thresholds at 0.5, 1, 2 and 4 kHz were compared with the corresponding thresholds measured using Bio-logic MASTER II and the Eclipse ASSR systems. The threshold differences and correlation with pure tone were measured and reliability was evaluated with Cronbachs α. In part I of the study, all subjects were included, in part II of the study, only mild hearing loss and normal hearing subjects were included.nnnRESULTSnIn part I, NB CE-Chirp ASSR revealed a significantly smaller difference in threshold than conventional ASSR, a better correlation and better reliability. However, lower frequencies of NB CE-Chirp tended to be less reliable than higher frequencies. In part II, NB CE-Chirp revealed smaller threshold differences than conventional ASSR. Both correlation scores and reliability values were generally lower in the part II results.nnnCONCLUSIONnNB CE-Chirp ASSR generally revealed more favorable outcomes. However, its reliability was reduced at lower frequencies and in patients with milder hearing loss.

Capacity of Rectified Vestibular Evoked Myogenic Potential in Correcting Asymmetric Muscle Contraction Power

Objectives Rectified vestibular evoked myogenic potential (rVEMP) is new method that simultaneously measures the muscle contraction power during VEMP recordings. Although there are a few studies that have evaluated the effect of the rVEMP, there is no study that has evaluated the capacity of rVEMP during asymmetrical muscle contraction. Methods Thirty VEMP measurements were performed among 20 normal subjects (mean age, 28.2±2.1 years; male, 16). VEMP was measured in the supine position. The head was turned to the right side by 0°, 15°, 30°, and 45° and the VEMPs were recorded in each position. The interaural amplitude difference (IAD) ratio was calculated by the conventional non-rectified VEMP (nVEMP) and rVEMP. Results The nVEMP IAD increased significantly according to increasing neck rotation. The IAD in rVEMP was almost similar from 0° to 30°. However, the IAD was significantly larger than the other positions when the neck was rotated 45°. When IAD during 0° was set as a standard, the IAD of the rVEMP was significantly smaller that the nVEMP only during the 30°rotaion. Conclusion Rectified VEMP is capable of correcting asymmetrical muscle contraction power. In contrast, it cannot correct the asymmetry if muscle contraction power asymmetry is 44.8% or larger. Also, it is not necessary if muscle contraction power asymmetry is 22.5% or smaller.

Comparison of treatment outcomes between 10 and 20 EEG electrode location system-guided and neuronavigation-guided repetitive transcranial magnetic stimulation in chronic tinnitus patients and target localization in the Asian brain

Abstract Objective: rTMS is a non-invasive method that applies a brief magnetic pulse to the cortex and is regarded as a possible therapeutic method for tinnitus control. However, it remains unclear whether the rTMS treatment effect would be the same in tinnitus patients receiving the 10–20 EEG-based target localization as in those receiving imaging-based neuronavigation target localization. Methods: We compared the treatment outcome of the 10–20 EEG-guided rTMS (Group 1) with that of the neuronavigation-guided rTMS (Group 2). Using the individual subjects MRI data and neuronavigation system, the coordinates of the AC relative to the 10–20 EEG system were identified in Asian and compared with those of Caucasian. Results: There was significant improvement in the THI and VAS scores in Group 1 and 2. However, there was no significant difference between the two groups. The location of the AC in Asians was significantly different to that in Caucasians. Conclusion: The 10–20 EEG coordinates of the AC in Asians were significantly different to those in Caucasians. To accurately aim for the AC in Asians, it is recommended that the rTMS be located 1.8u2009cm superior to the T3 and 0.6u2009cm posterior to the T3-Cz line. However, because the spatial resolution of the TMS is rather low, this difference probably was not reflected in the treatment outcome.

Facial nerve stimulation in the narrow bony cochlear nerve canal after cochlear implantation

To evaluate the correlation between a narrow bony cochlear nerve canal (BCNC) and facial nerve stimulation (FNS) after cochlear implantation (CI) and their underlying mechanisms and to predict the risk of FNS preoperatively.

Cochlear Implantation in Patients With CHARGE Syndrome

Objective: To determine the optimal surgical approach for cochlear implantation (CI) preoperatively based on the spatial relation of a displaced facial nerve (FN) and middle ear structures and to analyze clinical outcomes of CHARGE syndrome. Methods: Facial nerve displacement and associated deviation of inner ear structures were analyzed in 13 patients (17 ears) with CHARGE syndrome who underwent CI. Surgical accessibility through the facial recess was assessed based on anatomical landmarks. Postoperative speech performance and associated clinical characteristics were analyzed. Results: The most consistently identified ear anomalies were semicircular canal aplasia (100%), ossicular anomaly (100%), and vestibular hypoplasia (88%). Facial nerve displacement was found in 77% of cases (anteroinferior: 47%, anterior: 24%, inferior: 6%). The width of available surgical space around facial recess was significantly greater in cases of facial recess approach (2.85 ± 0.9 mm) than those of alternative approach (0.12 ± 0.29 mm, P = .02). Postoperatively, 53% achieved better than category 4 on the categories of auditory perception (CAP) scale. The CAP category was significantly correlated with internal auditory canal diameter (P = .025) and did not differ according to the applied surgical approach. Conclusion: Preoperative determination of surgical accessibility through facial recess would be useful for safe surgical approach, and successful hearing rehabilitation was achievable by applying appropriate surgical approaches.